1. Field of the Invention
The present invention generally relates to an information storage apparatus and, more particularly, to an information storage apparatus which records information on a disk-like recording medium having a plurality of zones each of which includes an alternating area to be substituted for a defective sector in which an error occurs.
A constant angular velocity (CAV) method is generally used for a disk drive apparatus which records information on a disk-like recording medium such as a magneto-optical recording medium or a phase-change optical recording medium. However, in recent years, zone constant angular velocity (ZCAV) method has become popular. In the ZCAV method, a recordable area of a disk-like recording medium is divided into a plurality of zones in a radial direction of the disk-like recording medium so that an angular velocity of the disk-like recording medium is changed between an operation performed on a zone located on an inner side and an operation performed on a zone located on an outer side of the disk-like recording medium.
Since a fixed number of sectors are provided in a physical track according to the CAV method, a recording density in a circumferential direction of the disk-like recording medium is decreased as recording operation progresses from an inner part toward an outer part of the disk-like recording medium. On the other hand, in the ZCAV method, since the recording area is divided into a plurality of zones in a radial direction so that an angular velocity can be set on an individual zone basis, a relatively constant recording density can be obtained irrespective of whether a recording operation is performed on an inner side or an outer side of the disk-like recording medium. Thus, the ZCAV method can achieve a higher recording density than the CAV method. However, such a high-density recording by the ZCAV method may create a defect in recorded information.
2. Description of the Related Art
In order to solve the above-mentioned problem, a conventional information storage apparatus such as a magneto-optical (MO) drive uses an alternating process. FIG. 1 is a flowchart for explaining a conventional substitution process. FIG. 2 is an illustration for explaining the conventional substitution process shown in FIG. 1.
In FIG. 1, it is assumed that an error occurs, in step S1-1, during an operation for writing information in a sector in a zone Z(N) (N=1, 2, 3, . . . ). It is determined, in step S1-2, whether there is an empty substitutional area AN in the zone Z(N) in which the information is to be written. If there in an empty substitution zone AN in the zone Z(N), the routine proceeds to step S1-3 so as to write the information in the empty substitutional area AN in the zone Z(N). On the other hand, if there is no empty substitutional area in the zone Z(N), the routine proceeds to step S1-4 so as to write the information in an empty substitutional area in the proceeding zone Z(N+1). This process is referred to as the substitution process.
However, the above-mentioned alternating process is not always effective when the ZCAV method is used. In the ZCAV method, since a high-density recording in a circumferential direction is performed, a margin with respect to a laser power or a magnetic field for recording is small. Accordingly, an error may easily occur on an outer side of a zone due to the small margin which is inherent to the ZCAV method. In such a case, an error may continuously occur even when the above-mentioned substitution process is performed.
As mentioned above, according to the conventional substitution process, when a defective sector is generated, the defective sector is first substituted by a substitutional area existing in the zone in which the defective sector exists. If all the substitutional areas in that zone have already been used for the alternating process, a substituting area in an adjacent zone is used.
Japanese Laid-Open Patent Application No. 9-82036 and Japanese Laid-Open Patent Application No. 4-3367 discloses a method for recording information in an alternating area adjacent to a zone of which all alternating zones have been used.
However, in the conventional information storage apparatus of the above-mentioned type, there is a high possibility that the substitution process is repeatedly performed with empty substitutional areas contained in the same zone since one of the substitutional areas to be used is selected from among substitutional areas contained in the zone which has a higher possibility to generate a defective sector.
Accordingly, it is possible that all of the substitutional areas in the same zone are consecutively used one by one. In such a case, there is a problem in that an access time for the disk-like a recording medium exceeds a predetermined time given by an operation system since the substitution process is repeated many times until all of the substitution process have been used. Additionally, the number of substitution process is increased and a number of defective sectors is also increased in a short time.
It is a general object of the present invention to provide an improved and useful information storage apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide an information storage apparatus in which a substitution process for substitutionally storing information when an error occurs in storing the information is prevented from being repeatedly performed with a substitutional area defined in the same recording zone so that wasteful execution of the substitution process is prevented.
In order to achieve the above-mentioned objects, there is provided according to the present invention an information storage apparatus adapted to store information on a recording medium having a plurality of recording zones, each of the recording zones being divided into a plurality of sectors, a substitutional area being defined in each of the recording zone so as to substitutionally store information when an error occurs in storing the information, the information storage apparatus comprising:
a defective sector detecting unit detecting a defective sector in each of the recording zones; and
a control unit controlling an operation for storing information so as to store the information, when a number of defective sectors included in a first one of the recording zones is greater than a predetermined value, in the substitutional area of a second one of the recording zones other than the first one of the recording zones in which the information is to be stored,
wherein the predetermined number is smaller than a maximum number of defective sectors includable in the substitutional area.
According to the present invention, if the predetermined number of defective sectors is generated in the one of the recording zone, it is determined that the one of the zone has a possibility of frequently generating a defective sector. Accordingly, the information to be recorded in the one of the zone after the number of defective sectors reach the predetermined value is stored in the substitutional area of another of the recording zones. Thus, the substitution process is prevented from being repeatedly performed in the one of the recording zones. This eliminates wasteful execution of the substitution process, and achieves a positive storage of information in a short time.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.